Protection of thyratron in impulse generating circuits



April 1948- E. D. BURLINGAME ET AL 38,962

PROTECTION OF THYRATRON IN IMPULSE GENERATING CIRCUITS Filed Aug. 7,1944 ww J y \J. o a mfi m. m mm as a w e71 s75 r CAVR Z0 0 X. 3% 5huwwNvw a w\ Rmwmvh w m; .w P} n 30 Q 250 5% l Patented Apr. 6, 1948Ernest ne Barnu Egg ertsvillfe mime w; Carlson, Depe'm Mfldison'wGiSnyder, andimamll 0. sum; Lama a;

assignom to; Goioniai; R adioiiffommflomhllut falo, N. Y.

This invention; reiatesttolthyratronpulse generating circuits andmore.particularlitb cireuits; of the type described employing anartificialjline; discharging v through a. thyratron in" response to:

partieularity in the i appended claims: our-mun ve uen itseir; howeveriboth as -to its prineipl arrdf vto* its particular: embodiments, willunderstood referring to the specifleatiom tri gering impulses upon thecontrorelectrode of accompanying drawing-on which the singleiflwei thethyratron.

In circuits" of this type difi'i'culties have been experiencedlin. thepast arising from failure of the thyrat-ronto deionize as and when itshould,

isa cirpuikdiagram of apparatus-in aeeordanc'e witl'i oin-1i'nyerrtion.

Referring npwvmore particularly to-tiiesdi'we ing;; trig ;geringimpulsesefi'om ;a sourcenot sliowm i. e.,immediatelyyafterdischarging-tire; artificial 0: 01" descrilied' and notnecesser ror: the untler line. This may cause failure of the apparatusand evenitsudestructionh 'lfhejeasonlfor this-is that the increase, incurrent over andjabflve the. normal operating, current may, not" be uflj ien to operatel lmtectille devices-such asrusesoncircult breakers,.butf is" us ally sufilcient; ,ifitic'ontinues, for, any length.oftime',,to burnoutithe powertransformer. 7.

Moreover, even, if j the. current dDes not: causestanding-or"our-invention; areimpressedtlirouili: transformer I II";which mayhave pflmairywi-n' s. I mg; I flux and secondary winding IUD";-coirtrol; circuit of tube oi the thyratron= V 111*; 'I liis'tiirie-maiyehave a cfiitm IIcr-controlelectrode l 'lig and anode HmItixe. catl iod'ejmay-s be connected? to ground andi itSi rid throughseeond'ary'win'ding loo -or; transit former III and tlirougl i a-suitable source; of fume failure of operating, parts; such" a:condition must? and potential? 9 to g-round'z' Tlie'i anodes be avoided;because while itremains tIieLap a ratus is unable to functionnormall'yfl: ez, to'dee liver pulses by discharging the artificial line"in response totriggeringimpulses;

It is amobje twf this. invention-to provide-am maticall y indieated as=resistance Iiitoiigr'oundfiaaizl paratus of a class described-finwhicliide=ioniZation of the tl'iyratron will take plaee unfailingiy atthe completion" of -the -discharge of tlie-artifi I cialline or within apredetermined? time-- after" completion thereof, shouldde-ionizati'onnottairea serilied' in detaili Theilineimay be clrargefrom:

place.

It is a: further object ofthis-invention-to provide acircuit" of the"class described which will? not be destroyed or. rendered'inoperativeshould= I Iii anayrbercormected to th e inputof the-artificial: lineI2made uppfiinductancewlls and capacities I'l The commonterm-inal'lofiali capacitiessmay be' 'connected tliroughtheoutput load diagra;

tlrougli inim yscases this may bezartransiormen.

Sinee-ttie -design-and' oonstruetion of artiiiciaii. lines lravir'rg-anyparticular characteristics weiii unclerstood it the art,- I this isnoti showmor adezwpowerisource; not shown through powertriatermeri' Iti-liavina primary windings IBwrarrdis ondaryewinding I 61) 1 through:rectifierz, I I msw svemmae l mandamus-2| laiandsthroug'n;

normal tie-ionizationof thethyratron' not occur-e ch ifie re istance I9:to the-2 artificial! line?! 1 after completion OfthGdi'SlfiBlgGi- It isstill a-iurther-obiect of this: invention to: provide apparatus oftheclass-dscribed'whicin is simple and economical to"construct" and" iailing in operation;

It is-still further an object of this'dnventiomtmprovide a circuit ofthe class described whieli wiiiautomaticallyreset itself "tonormalconditio'ns upon operation of the protective devicez Flltercondenser l8"may:beiprovidedifronr cathodes I "Ie -tMgroundi In =normali'operation:tlrestriggere ingaimpulse impressed umn magma :otzth'e: tubes: I i isirfiicient to cause ionization: and tliusz: toe: 1; perm-ittliedisohargeof theiartifi'eial iline through; the -tube lii As wiil'rbeunclerstoedgt the duratiom am amplitude 0r thecurrent 1pui$e derivedifroma. the artifieial lines iss-controliedibysrtheiconsti'ust ents-thereoffand is independentfotitl're amzplitude It is still i a Ifurther object of this invention to ueanddumtlon of tiie;triggering-impulses;

provide a circuit of the-=class= described; embodying; a relay whicliwill operate toflimit tfie cur-*- rent flow should: normalde-ionizatiorr or thethyratronnot take place ami in wlricli' -the op the thyratron ls de ioni-zeari thei plate-a voltage may be asihigh:ass5',0001rvolts;v butrwhex ri tlie tliyratrorr isionizewithis;.voltageimayz'droptasi low 'as lfi -ivoitssbut this'emay beinsuifibientzxtet eration of therelay-isdefinitely certaim andeen Icauses de lonizati an-x on the? thyratrorr's after? the? tireiy freefrom chatter:-

Still other obj este and ada rantagesor our: in vention willhie-apparent fromihe specifieationst The '--features of IIOVBltYEsWhiCh"we believe to be lineman; discharged-:3. If :thislwhapperis; .theihwrwtron will remain ionized and will be unresponsivetottiriggeringrimpulses wd:2thercontinuemflowsof heavy; current ahcvea;arms-1' beyond? that arequiztedst characteristic of our invention areset fortlr witli- 55abymormalicperatlemxmay'resuit in burningiouti thepower transformer I6. To prevent this we provide a voltage divider whichmay be made up of resistances 20 and 2| connected from the anode I la toground. Resistance 2| may be shunted by condenser 22 and the voltagedrop across resistance 2| may-be impressed upon the relay tube 23." Thismay be a tube of the 6J5GT type and may have cathode 230, controlelectrode 239, and

anode 23a.

Cathode 23c maybe connected to ground through resistance 24 and theanodezaa voltage; also bleeder resistance 25 maybe connected from thesource of plate; yoltage'to the cathode side of resistance 24. Front'andback contacts 26 and 2612 may be provided for relay 26, to be engaged byarmature 26a and when the armature 26a is closed on front contact 26)'a'cir cuit is established short-circuiting resistance" 21 the platevoltage upon this tube may be as high 3 as 5,000 volts. Under thesecircumstances a substantialpositive voltage is maintained on the controlelectrodeof tube 23 with respect to oath ode,'and tube 23 draws fullspace current, which flows through the energizing winding o f-relay-2t':and holds the' armature 26a against front contact 26] therebyshort-circuiting resistance 21 and permitting full flow of currentthrough the power transformer, thereby maintaining the arti-I ficiallinei2 charged. When a triggering impulse is received, the tube I I ionizesand the artificial line I2 begins to discharge. After his completelydischarged; the voltage upon the anode-I Ia may drop to as low as volts,but under certain conditions the thyratron may not de-ionize because asuflicient flow of plate current stilloccurs; This must be reduced stillfurther in orderto de-ionize the tube. When thevoltage uponthe anode IIa drops, the voltage upon the control electrode of tube 23 likewisedrops to a very'low value in same ratio and this is made sufficient tocause tube 23 to cut 01T and therebyrelease armature 26a which may. bebiased to back contact and; therefore, opens, removing the short-circuitaround resistance 21 and inserting this resistance in series with powertransformer primary I611. The value of this resistance is so chosen thatit limits the currentflowing through thyratron II to a value less thanthe critical value required to maintain ionization. The tube IIthereupon'de-ionizes, current flowthrough the'tube stops, and the platevoltage begins to rise and line I2 begins to charge. As the platevoltage rises; the voltage upon the control electrode 23g'of tube 23rises and this tube again'begins to pass current after the controlelectrode to cathodepotential goes above cutoff value,-whereupon space,current once more flows through this tube. Relay 26 is energized,armature 26a is moved to front contact 26], resistance, 21short-circuited, and conditions return to normal'. Resistances and 2|'are made relatively high T so that when the voltage at the plate of thethyratron II is at its normal high value, the

current drawn by the grid of tube 23 is kept down to a reasonable value,say a fraction of a milliampere. Also, the ratio of resistance 20 toresistance 2| is made relatively high so that only 5 a-small portion ofthe plate voltage of the thyrai may be connected to one terminal ofthe-relay winding of relay 26, thence to a source ofplate g tron isapplied to'the'tube 23. Preferably the tube 23 is operated at zero biasfor high positive ;vo l tage on the grid, thereby promoting'uniformitytoperation and protection. Capacity 22 is emoiplo'yed to eliminate thepossibility of relay chatter-during normal operation of the thyratron II where the ionization lasts for only a fraction of j, amillisecond.

, ,ii? .J-In order to complete the disclosure herein, but 5 not-byway oflirni'tation, the following values are given:

ResistanceI9; ';;;"20,000 Ohms 7 Resistance, 6' Megohms Resistance 2|0.47 Megohm Resistance 24 3,300 Ohms Resistance 25 27,000v OhmsResistance 21 a 400 Ohms Inductance I3 5 Microhenries 0.002 Microfarads(eitcept the terminating ca- 5 a ac y pacity which is Y. 0.004) CapacityI8 1 Microfarad Capacity 22 0.1 ..Microfarad The artificial lineemployed has a characteristic impedance Z0 equals50 ohms. Electricallength equals one millisecond. Outputpulse length equals 2 milliseconds.'While We have shownand described certain preferred embodiments of ourinvention, it will be apparent that modifications and changes may bemade without departing from the spirit and scope of our, invention, aswill be clear tothose' skilled in the art.

In the specification we have explained the principles of our inventionand the best mode in.

;WhiCh we have contemplated applying those prin- 59;;vention ordiscovery.

ciples, so, as to distinguish our invention from other inventions; andwe have particularly pointedout and distinctly claimed the part,improvement, or combination which we claim as our in- We claim:

1. In a pulse generating circuit, in combina tion, a storage element,means for charging said element, a thyratron, having a cathode, a con- 5trol electrode, and an anode, connected to said element for dischargingthe same, means for applying triggering impulses to a control electrodeof said thyratron, and means operated by the potential differencebetween the cathode and ang ode of said thyratron and responsive tofailure of said thyratron, to de-ionize after said storage elementisdischarged, for limiting the current through said thyratron to a valueless than that required to maintain ionization therein.

2. In a pulse generating circuit, in combination, a storage circuitcomprising capacity, a thyratron; having a cathode, a control electrode,and an anode, connected to said storage circuit for discharging thesame, means for applying triggering impulses to said control electrode,and means operated by the potentialdiiference between the cathode andanode of said thyratron and responsive to failure of said thyratron todeionizev after said storage circuit is discharged, 5 ,for limiting thecurrent through said thyratron aeeaeca to a value less than thatrequired, to maintain ionization therein.

3. In a pulse generating circuit, in combination, an artificial line,means for charging said artificial line, a thyratron, having a cathode,a control electrode, and an anode, connected to said artificial line fordischarging the same, means for applying triggering-impulses to saidcontrol electrode, and means operated by the potential differencebetween the cathode and anode of said thyratronandresponsive to failureof said thyratron to de-ionize after said artificial line is discharged,for limiting the current through said thyratron to a value less thanthat required to maintain ionization therein.

4. In a pulse generating circuit, in combination, an artificial line,means for charging said artificial line, a thyratron, having a cathode,a control electrode, and an anode, connected to said artificial line fordischarging the same, means for applying triggering impulses to saidcontrol electrode, and means operated by the potential differencebetween the cathode and anode of said thyratron and responsive tofailure of said thyratron to de-ionize after said artificial line isdischarged, for limiting the current through saidthyratron to a valueless than that required to maintain ionization therein, said lastmentioned means comprising a relay and a control tube for operating saidrelay, said control tube being responsive to the plate voltage of saidthyratron.

5. In a pulse generating circuit, in combination, an artificial line,means for charging said artificial line, a thyratron, having a cathode,a control electrode, and an anode, connected to said artificial line fordischarging the same, means for applying triggering impulses to saidcontrol electrode, and means operated by the potential difierencebetween the cathode and anode of said thyratron and responsive tofailure of said thyratron to de-ionize after said artificial line isdischarged, for limiting the current through said thyratron to a valueless than that required to maintain ionization therein, said lastmentioned means comprising a short-circuited resistor in the currentsupply path for said thyratron and means for inserting said resistor inresponse to failure of said thyratron to de-ionize after discharge ofsaid artificial line.

6. In a pulse generating circuit, in combination, an artificial line,means for charging said artificial line, said means comprising a powersource and a rectifier, a thyratron, having a cathode, a controlelectrode, and an anode, connected to said artificial line fordischarging the same, means for applying triggering impulses to saidcontrol electrode, and means operated by the potential differencebetween the cathode and anode of said thyratron and responsive tofailure of said thyratron to de-ionize after said artificial linethrough said thyratron to a value less than that required to maintainionization therein.

7. In a pulse generating circuit, in combination, an artificial line,means for charging said artificial line, said means comprising a powersource and a rectifier and a resistance in series with said powersource, a thyratron, having a cathode, a control electrode, and ananode, connected to said artificial line for discharging the same, meansfor applying triggering impulses to said control electrode, and meansoperated by the potential difierence between the cathode and anode ofsaid thyratron and responsive to failure of said thyratron to de-ionizeafter said artificial is discharged, for limiting the current 6' alineis discharged, for limiting the current throu h said thyratron to avalue less than that required to maintain ionization therein, said meanscomprisinga relay arranged to short out saidxresistance during normaloperation and to insertsaid resistance upon failure of said thyratronito de-ionize after said artificial line is discharged.

8. Ina pulse generating circuit, in combinaton, an artificial line,means for charging said artificial line, said means comprising a powersource and a rectifier, and a resistance in series with said powersource, a thyratron, having a cathode, a control electrode, and ananode, connected to said artificial line for discharging the same, meansfor applying triggering impulses to said control electrode, and meansoperated by the potential difference between the cathode and anode ofsaid thyratron and responsive to failure of said thyratron to de-ionizeafter said artificial line is discharged, for limiting the currentthrough saidthyratron to a value less than that required to maintainionization therein, said means comprising a relay for short circuitingsaid resistance during normal operation, and a control tube responsiveto the plate voltage of said thyratron for operating said relay.

9. In a pulse generating circuit, in combination, an artificial line,means for charging said artificial line, said means comprising atransformer and a rectifier and a protective resistance in series withthe primary of said transformer, a thyratron, having a cathode, acontrol electrode, and an anode, connected to said artificial line fordischarging the same, means for applying triggering impulses to saidcontrol electrode, means operated by the potential difierence betweenthe cathode and anode of said thyratron and responsive to failure ofsaid thyratron to deionize after said artificial line is discharged, forlimiting the current through said thyratron to a value less than thatrequired to maintain ionization therein, said last mentioned meanscomprising a relay for short circuiting said protective resistance, acontrol tube arranged to energiZe said relay to short circuit saidprotective resistance when the plate potential of said thyratron exceedsa predetermined value, and a voltage divider connected to the plate ofsaid thyratron for applying to said control tube a portion of the platevoltage of said thyratron.

10. In a thyratron protecting circuit, in combination, a thyratron,having a cathode, a control electrode, and an anode, a power supply forsaid thyratron, a protective resistance in the circuit supplying currentto said thyratron, a voltage divider connected between cathode and anodeof said thyratron, a control tube, a connection for applying a portionof the voltage of said voltage divider to said control tube, and a relayin the output circuit of said control tube for short circuiting saidprotective resistance, said age across said voltage divider upon saidcon trol tube, and a relay in the output circuit 01 REFERENCES CITEDsaid control tube, the constants of said control The following e er esare 0! reco in tube and its associated circuits being so chosen file Ofthis P te t:

that said protective resistance short circuited 5 UNITED STATES PATENTSfor values of plate voltages of said thyratron exceeding a predeterminedvalue and in circuit for Number Name te values less than saidpredetermined value. 3 5 Foulke July 1934 ERNEST BURLINGAME 2,088,548Chauveau July 2'7; 1937 ROBERT CARLSON. v 10 2,102,951 Hackenberg Dec.21, 1937 M DI N NICHOLSON, JR, 2,282,108 W mann Ma-y5. 1942 MAXWELL C.SCOTT.

